Small business tax returns: which form your company files and when

If you are working out how to file for your business, almost every practical question is decided by one thing: what the entity is for tax purposes. That determines which return you file, which month it is due, and whether the company files at all or the income simply lands on your personal return.

Get that wrong and everything downstream is wrong. The most common version is a company that treats its return as due in April when it was actually due in March, which is how a business with no tax owed accrues a penalty anyway.

Here is the routing by entity, the filings that exist even when there is no revenue, and the obligations that run separately from the federal return.

Your entity decides the form and the deadline

For a calendar-year business, the pattern is:

Sole proprietorship or single-member LLC. No separate return. Business income and expenses go on Schedule C, filed with your personal Form 1040 in April. Self-employment tax is calculated on Schedule SE alongside it.

Partnership or multi-member LLC. Form 1065, due March 15. The partnership pays no income tax itself and issues a Schedule K-1 to each partner, who reports their share personally.

S corporation. Form 1120-S, also due March 15. Same pass-through structure and same K-1 mechanism. This is the one people get wrong, because S corporations are corporations and the instinct is to file them with the C corporations in April.

C corporation. Form 1120, due April 15. The company pays tax at the corporate level on its own profits.

The two pass-through returns share a deadline a month earlier than the corporate and personal ones, and the reason is structural: owners need their K-1s before they can file personally.

If your business uses a fiscal year rather than a calendar year, these dates are not calendar dates at all. They are the fifteenth day of the third month after year end for partnerships and S corporations, and the fifteenth day of the fourth month for C corporations.

Zero revenue does not mean zero filing

This is the most expensive misunderstanding for a company in its first year or two.

A C corporation files Form 1120 whether or not it traded, earned anything, or opened a bank account. Existence creates the obligation. Partnerships file if they had any income or deductions, which a dormant entity with a few expenses does.

The version that costs the most involves foreign ownership. A US LLC with a single foreign owner is disregarded for income tax, which leads people to conclude there is nothing to file. There is. That entity files a pro forma Form 1120 together with Form 5472 to report transactions with its foreign owner, including capital contributions and loans. The penalty for missing it applies per form, per year, regardless of revenue or tax owed, and it is substantial.

Inkle files Form 1120, Form 1065, and personal returns on Form 1040, along with the Form 5472 reporting that attaches to a foreign-owned entity, which is the filing most often discovered late because nobody expects a dormant company to owe anything.

An extension moves the filing date, not the payment date

Businesses request an extension on Form 7004, and individuals on Form 4868. Both are granted automatically when filed on time, with no reason required.

They buy six months. A partnership or S corporation return moves from March to September, and a C corporation or personal return moves from April to October.

Two things the extension does not do. It does not extend the time to pay, so tax owed is still due on the original date and interest runs from there. And extending a pass-through return does not extend the owners' personal returns, which is a trap for anyone waiting on a K-1: the partnership has until September, and the partner still has to either file in April or extend separately.

Credits reduce tax, deductions reduce income

These get described interchangeably and they work differently, which matters when you are estimating what something is worth.

A deduction reduces taxable income. Its value depends on your rate, so a $10,000 deduction at a 21% rate is worth $2,100.

A credit reduces tax directly. A $10,000 credit is worth $10,000, whatever your rate. That is why credits are rarer and more tightly conditioned.

Some credits are refundable, meaning they can produce a payment when they exceed your tax. Most business credits are not, and instead carry forward to future years when you have tax to use them against. A company with no taxable income does not lose a nonrefundable credit, but it does not benefit from it this year either.

Incidentally, the energy efficiency provision for commercial buildings that appears on most credit lists is a deduction rather than a credit.

The information returns are due before your return

Your own return is not the first deadline of the year.

Forms W-2 for employees and Forms 1099-NEC for contractors are generally due by the end of January, both to the recipient and to the government. They carry their own penalties, assessed per form, which increase the longer they are late.

This catches companies that think of tax season as a single event in March or April. By the time you are assembling your return, the information return deadline has already passed.

State and franchise obligations run separately

Filing federally settles nothing at state level, and the two have no relationship.

Most states require their own income or franchise return, on their own schedule. Delaware franchise tax and the annual report are due March 1 for corporations, which is before every federal deadline in this post and is not a tax return at all. Any state where you have employees, an office, or sufficient economic presence will expect a registration and a filing of its own.

The failure mode is not usually a decision. It is a company that files federally, considers the year closed, and discovers a state obligation through a penalty notice.

The bottom line

Start from the entity, because it decides the form and the month, and the single most common error is filing a pass-through return on the corporate calendar. Diarize March 15 separately from April 15 if your company is a partnership or an S corporation. Assume you file even with no revenue, particularly if the company has a foreign owner, since that is where the penalties are largest and least expected. Remember that an extension buys filing time and not payment time, and that extending the company return does nothing for the owners' personal ones. And treat state and franchise obligations as a separate calendar rather than as an extension of the federal one.

Frequently asked questions

Which tax form does my business file?

A sole proprietorship or single-member LLC files Schedule C with the owner's Form 1040. A partnership or multi-member LLC files Form 1065. An S corporation files Form 1120-S. A C corporation files Form 1120. The entity's tax classification decides this, not its legal form, so an LLC could be filing any of several of these.

When is my business tax return due?

For calendar-year businesses, partnerships and S corporations file by March 15, and C corporations and individuals by April 15. For a fiscal year, the rule is the fifteenth day of the third month after year end for pass-throughs and the fourth month for C corporations.

Do I have to file if my company made no money?

Usually yes. A C corporation files regardless of activity. A partnership files if it had any income or deductions. A foreign-owned single-member LLC files a pro forma Form 1120 with Form 5472 even though it owes no income tax, and the penalty for missing that applies regardless of revenue.

Does an extension give me more time to pay?

No. An extension moves the filing deadline by six months and nothing else. Tax owed remains due on the original date, with interest accruing from then. Extending a partnership or S corporation return also does not extend the owners' personal returns.

What is the difference between a tax credit and a deduction?

A deduction reduces taxable income, so its value depends on your tax rate. A credit reduces tax owed directly, dollar for dollar. Most business credits are nonrefundable, meaning they cannot take your tax below zero, but unused amounts generally carry forward.

What else is due besides the tax return?

Information returns come earlier. Forms W-2 and 1099-NEC are generally due by the end of January, with their own per-form penalties. State income or franchise returns run on separate schedules, and Delaware franchise tax and the annual report are due March 1 for corporations.